To Grow to Be a Man – Growth Hormone vs. Testosterone

Dr. Alexander W. Pastuszak, a resident physician at Baylor College of Medicine

Often when you hear the words “Growth Hormone,” it brings up images of bodybuilders, and frequently the use of growth hormone (GH) outside of medicine is focused on increasing lean body mass and decreasing fat mass, much the same as the use of testosterone outside of its normal clinical applications. However, GH remains an essential hormone in our body’s milieu, and without it, not only do people grow slowly, they can have difficulties with maintaining lean body mass, can develop low bone mineral density, which increases the risk for fractures, and can have heart problems, which can increase the risk of death 2-fold in GH-deficient individuals. People with low GH can also have low energy, poor concentration, memory loss, increased fat mass, and changes in cholesterol that may increase the risk of heart disease. Take note that many of these symptoms are the same as those associated with low testosterone, and studies have shown that testosterone and GH are linked – decreases in testosterone result in decreases in GH, and vice versa.

So how can we tell which hormone does what, and to what extent? Besides the obvious differences in blood hormone levels, the best way to determine what these hormones do would be to compare their effects in a side-by-side manner. However, there are very few studies directly comparing the results of supplementation of GH together with testosterone, and these studies have focused mainly on changes in lean body mass and fat mass and have looked mainly at an older population. When looking at the results of all of these studies together, GH has a more dramatic effect on increasing lean body mass and decreasing fat mass than testosterone. In addition to increases in lean body mass and decreases in fat mass, GH also has numerous other beneficial effects on the body, when used as a treatment for GH deficiency. These include decreases in total cholesterol and LDL cholesterol (the “bad” cholesterol), apolipoprotein B (ApoB) and C-reactive protein (CRP). All of these are markers for increased cardiovascular disease risk, and lower levels of these markers suggest a decreased risk of disease. Improvements in heart function as a result of GH administration have also been demonstrated in GH-deficient individuals, and may decrease the risk of death from heart disease in this population. Also, GH administration results in improvements in bone mineral density.

Despite these beneficial effects, GH has also been shown to increase fasting insulin and glucose levels, potentially increasing the risk for diabetes in individuals taking GH. Several studies have also shown an increase in hemoglobin A1c as a result of giving GH, which is a long-term measure of glucose control, an increase that suggests poor glucose control and increased risk for diabetes. However, no cases of diabetes have been linked directly to GH supplementation, so the jury remains out on this.

What all of this means is that giving GH to deficient individuals improves heart function and may decrease the risk of cardiovascular disease. Though GH may increase the risk of diabetes, this ultimately this needs to be further studied. In addition, since all of the above results were obtained from a GH-deficient population, the same conclusions are unlikely to apply to those who use GH for bodybuilding purposes. As a result, it’s difficult to comment on how safe and effective GH is in the athletic setting.

What about testosterone? We know a lot about the effects of testosterone, as it’s gotten quite a bit of air-time in this blog (see “More important info on low testosterone,” “Testosterone – Which Form is Right For You?”) and elsewhere of late, but testosterone has many of the same effects as GH does, from improvements in lean body mass, fat mass, and bone mineral density, to potentially beneficial effects on cardiovascular status, data that conflict with prior data indicating that testosterone supplementation increases the risk of cardiovascular disease.

If the symptoms of GH and testosterone deficiency are similar, how do we know whom to give which hormone to and when? Your doctor will perform blood tests to check your testosterone and GH levels. If we find that your testosterone level is below a certain cutoff and that you have symptoms of testosterone deficiency (see “Testosterone – Which Form is Right For You?”), treatment will likely be started. For GH, blood levels of Insulin-like Growth Factor 1 (IGF-1), a surrogate blood marker for GH, are measured. If you have blood levels of IGF-1 lower than a certain value, further evaluation for GH deficiency is usually pursued to confirm that your body doesn’t make enough GH, and if this is the case, then treatment with GH may be started. However, while testosterone deficiency, which affects approximately 40% of all men, appears to be much more common than GH deficiency (1/10,000 individuals), not everyone tests for GH deficiency in the setting of the above symptoms. While I’m not saying that testing for GH deficiency in men with the symptoms described above is necessary, it’s something that we should keep in the backs of our minds, and ultimately, we need to study the relationship between testosterone and GH in more depth.

The take home message here is that both testosterone and GH deficiency share a common set of symptoms and negative effects on the body, and the two hormones are linked together in how they are regulated by your body. Therefore, if your doctor looks for low levels of one, he or she should consider assessing the other as well, since replacement of either hormone has clear beneficial effects on the body in at least the short term.